Chelants or chelating agents are compounds which form coordinate-covalent bonds with a metal ion to form chelates. Chelates are coordination compounds in which a central metal atom is bonded to two or more other atoms in at least one other molecule or ion, called a ligand, such that at least one heterocyclic ring is formed with the metal atom as part of each ring.
Chelating agents for metal ions, such as calcium, magnesium, iron, and manganese, are desired for a wide range of technical fields. Examples of fields of application and end-uses are detergents, in electroplating, in water treatment, photography, textile industry, paper industry and also various uses in pharmaceuticals, cosmetics, foodstuffs and plant nutrition. Some of these activities may result in the chelating agents entering the environment. For example, agricultural uses or use in detergents may result in measurable quantities of the chelants in water.
While some chelants are particularly useful for removing metal scaling, they can be susceptible to solidification or crystallization at low temperatures. For instance, iminodiacetic acid derivatives are known to possess metal sequestering properties. But concentrated solutions of the disodium salt of 2-hydroxyethyl iminodiacetic acid, a particularly useful derivative of iminodiacetic acid are observed to crystallize, in whole or in part, in cold weather conditions. Unfortunately, the solidification is unpredictable and the determining causes of solidification have been difficult to ascertain. Consequently, in operations where the chelant is used in cold climates this random and unpredictable behavior results in undesirably high amounts of chelant that is unusable at the time it is needed. Thus, it would be useful to provide chelant compositions that have suppressed solidification or crystallization at low temperatures.